1. Field of the Invention
The present invention relates to a semiconductor device fabrication apparatus and a method for filling a gap using the same, and more particularly, to a high density plasma chemical vapor deposition apparatus that is capable of filling a gap of a high aspect ratio without a void and its method using the same.
2. Description of the Background Art
The gap presented in the descriptions defines a collapsed portion compared with a peripheral pattern during a semiconductor device fabricating processes, such as a trench which is formed between adjacent individual elements or between metal wiring or formed in a STI (Shallow Trench Isolation) process.
As the semiconductor device becomes more integrated, the distance between individual elements or the distance between the metal wiring or the separation region, that is, the width of the trench, is accordingly reduced. Thus, the aspect ratio of the gap formed during the semiconductor device fabricating processes becomes great and it is not easy to fill the gap of a high aspect ratio without a void.
Recently, a technique that the gap of a high aspect ratio is filled with an insulation material by using a high density plasma (referred to as xe2x80x98HDPxe2x80x99, hereinafter) chemical vapor deposition (CVD) is widely employed. In a thin film deposition process using the HDP CVD method, since the process of depositing a thin film and an etching process by sputtering are simultaneously performed, the gap of a high aspect ratio can be effectively filled without a void.
The HDP can be formed by applying appropriately a radio frequency of a single frequency band or a radio frequency of several frequency bands to a coil antenna surrounding a vacuum chamber. Thusly formed plasma is called ICP (Inductively Coupled Plasma).
FIG. 1 is a sectional view for explaining a gap filling method by using a PECVD (Plasma-enhanced CVD) method.
As shown in the drawing, aluminum patterns 20 are formed on a wafer 10 and a gap 30 between the aluminum patterns 20 is filled with a silicon oxide 40.
In this respect, if the step coating of the silicon oxide film 40 is not good, as the deposition process of the silicon oxide film 40 proceeds, the entrance of the gap 30 is clogged by the silicon oxide film 40 before it is wholly filled with the silicon oxide film 40, resulting in that the void xe2x80x98Axe2x80x99 is formed in the gap 30.
This phenomenon is observed to be more serious as the space between the aluminum patterns 20 is narrow, that is, the aspect ratio of the gap 30 is increased. But, by using the HDP CVD method, the phenomenon can be remarkably reduced.
FIG. 2 is a schematic view of a HDP-CVD apparatus in accordance with a conventional art.
As shown in the drawing, a vacuum chamber 11 provided with the gas inlet 21a and a gas output 21b includes an upper container 11a and a lower container 11b. The upper container 11a is made of quartz and formed in a dome shape.
A suscepter 31 is installed in the vacuum chamber 11 and a wafer 41 is mounted on the upper surface of the suscepter 31. A wafer chuck 31a is installed at a periphery of the wafer 41 mounted on the upper surface of the suscepter 31 to prevent the wafer from moving on the upper surface of the suscepter 31.
A coil antenna 51 is installed at the outer wall of the upper container 11a to receive an RF power from an RF generator (not shown). When an RF power of a single frequency band or an RF power of various frequency bands is applied to the coil antenna 51, an HDP 61 is formed at the upper portion of the wafer 41 of the space within the vacuum chamber 11.
The conventional HDP-CVD apparatus is mostly used to fill the gap of a trench in the STI process or to fill the gap between the aluminum wiring, a cooling unit (not shown) is installed in the suscepter 31.
That is, since the temperature of the wafer 41 naturally goes up to about 700xc2x0 C. due to the HDP energy during the thin film deposition process using plasma, a water cooled tube (not shown) in which a cooling water flows is installed in the suscepter 31 to protect the aluminum wiring formed on the wafer 41.
FIGS. 3A through 3D are sectional views for explaining a gap filling method using the HDP-CVD apparatus of FIG. 2.
FIG. 3A is a sectional view for explaining a process for forming a silicon oxide film 130.
First, when aluminum patterns 120 are formed on the wafer 110, a gap 125 is formed between the aluminum patterns 120. Next, SiH4 gas, O2 gas and Ar gas are mixedly put in the HDP CVD apparatus of FIG. 2, the RF power is applied to the coil antenna 51 to change the gases to a HDP state, and a silicon oxide film 130 is deposited on the resulted structure where the aluminum pattern 120 has been formed.
At this time, in the process of depositing the silicon oxide film 130, since the temperature of the wafer 110 naturally goes up to about 700xc2x0 C. due to the HDP energy. Thus, in order to thermally protect the aluminum pattern 120, the suscepter on which the wafer is mounted is cooled.
Since the HDP has a high energy, a phenomenon occurs that the silicon oxide film 130 is deposited on the wafer, and at the same time, the deposited silicon oxide film 130 is sputtered by the ions existing in the plasma.
In this respect, since the etching rate of the silicon oxide film 130 is even more rapid at the corner portion of the aluminum pattern 120 than at the other portion, the silicon oxide film 130 has a profile of a 45xc2x0 sloped face xe2x80x98Bxe2x80x99 at the corner portion of the aluminum pattern 120.
Accordingly, even though the deposition process of the silicon oxide film proceeds, the phenomenon of clogging the entrance of the gap 125 does not occur, so that, unlike the case by the conventional PECVD, the gap 125 between the aluminum patterns 120 is filled without a void as shown in FIG. 3B.
However, if the gap 125 becomes narrow, the phenomenon that the silicon oxide which has been etched by sputtering is redeposited, making it difficult to fill the gap without a void even with the conventional HDP-CVD method.
In the case that the silicon oxide which has been etched is redeposited, as shown in FIG. 3C, an overhang portion xe2x80x98Cxe2x80x99; is formed at the silicon oxide film 130 at the corner portion of the aluminum pattern 120, resulting in a problem that, as in the case using the conventional PECVD, the entrance of the gap 125 is first closed to form a void within the gap 125 before the gap 125 is completely filled with the silicon oxide film 130.
In order to solve the problem, if the strength of the plasma is increased, overetching takes place that even the corner portion of the aluminum pattern 120 is etched as shown in FIG. 3D, disadvangateously damaging the aluminum pattern 120.
Thus, in order to fill the narrow gap 125 without a void by using the HDP-CVD method, it is critical to precisely control the redeposition rate of the sputtered silicon oxide.
Therefore, an object of the present invention is to provide a high density plasma chemical vapor deposition apparatus that is capable of filling a gap without a void, and a gap filling method using the apparatus.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a high density plasma chemical vapor deposition apparatus including: a vacuum chamber provided with an inlet and an outlet for a reaction gas; a suscepter positioned within the vacuum chamber to mount a wafer thereon, the suscepter having a wafer chuck at its upper surface to prevent the wafer from moving horizontally; a coil antenna surrounding the upper outer wall of the vacuum chamber; an RF generator for applying an RF power to the coil antenna; and a heating unit for heating the wafer mounted on the suscepter.
In the high density plasma chemical vapor deposition apparatus of the present invention, the upper portion of the vacuum chamber may be formed in a quartz dome, and a bell jar may be installed outside the quartz dome to cover the quartz dome.
In the high density plasma chemical vapor deposition apparatus of the present invention, the heating unit is installed at least at one of the inside of the suscepter, the inside of the wafer chuck and the bell jar, and its heating element is preferred to be a resistance wire, but in case that it is to be installed at the bell jar, the heating element may be an infrared ray lamp.
The high density plasma chemical vapor deposition apparatus of the present invention may further includes a remote plasma generator installed outside the vacuum chamber; and a plasma transfer tube for connecting the remote plasma generator and the vacuum chamber to transfer the plasma generated in the remote plasma generator to the vacuum chamber.
To achieve the above object, there is also provided a gap filling method in which a trench electrically isolating transistors or a wafer having a gap between gate electrodes made of a polycrystalline silicon is heated in advance to have the temperature of 300xcx9c700xc2x0 C. and the gap is filled with an insulation film by using a HDP CVD apparatus.
In the gap filling method of the present invention, the insulation film is one of USG (undoped silicate glass) film, a PSG (phosphorous silicate glass) film a BPSG (boron phosphorous silicate glass) film and an O3-TEOS (tetra-ethyl-ortho-silicate) film, and the density of the plasma in the HDP CVD process is preferably 1011 to 1012 ion/cm3.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.